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2 years ago

Number of neutrons for 9BE4

Chemistry

1 answer:

GREYUIT [131]2 years ago

8 0

Mass number - # of protons = #neutrons, so I would say the answer is 5

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1. What are commonly called as "shooting stars"?

nydimaria [60]

Answer:

Explanation:

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3 years ago

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It takes 495.0 kJ of energy to remove 1 mole of electron from an atom on the surface of sodium metal. How much energy does it ta

Zigmanuir [339]

Answer:

$\lambda=241.9\ nm$

Explanation:

The work function of the sodium= 495.0 kJ/mol

It means that

1 mole of electrons can be removed by applying of 495.0 kJ of energy.

Also,

1 mole = $6.023\times 10^{23}\ electrons$

So,

$6.023\times 10^{23}$ electrons can be removed by applying of 495.0 kJ of energy.

1 electron can be removed by applying of $\frac {495.0}{6.023\times 10^{23}}\ kJ$ of energy.

Energy required = $82.18\times 10^{-23}\ kJ$

Also,

1 kJ = 1000 J

So,

Energy required = $82.18\times 10^{-20}\ J$

Also, $E=\frac {h\times c}{\lambda}$

Where,

h is Plank's constant having value $6.626\times 10^{-34}\ Js$

c is the speed of light having value $3\times 10^8\ m/s$

So,

$79.78\times 10^{-20}=\frac {6.626\times 10^{-34}\times 3\times 10^8}{\lambda}$

$\lambda=\frac{6.626\times 10^{-34}\times 3\times 10^8}{82.18\times 10^{-20}}$

$\lambda=\frac{10^{-26}\times \:19.878}{10^{-20}\times \:82.18}$

$\lambda=\frac{19.878}{10^6\times \:82.18}$

$\lambda=2.4188\times 10^{-7}\ m$

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1 m = 10⁻⁹ nm

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2 years ago

How many moles are in 987 grams of Ra(OH)2

ra1l [238]

Molar mass Ra(OH)2 = 260 g/mol
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3 years ago

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What is the capillary rise of ethanol in a glass tube with a 0.1 mm radius if the surface tension of ethanol is 0.032Jm2 and the

sweet [91]

Answer: The capillary rise(h) in the glass tube is = 0.009m

Explanation:

Using the equation

h = 2Tcosθ/rpg

Given

Contact angle, θ = Zero

h = height of the glass tube=?

T = surface tension = $0.032J/m^2$

r = radius of the tube = 0.1mm =0.0001m

p= density of ethanol = $0.71g/cm^3$

g= $9.8m/s^2$

h = $(2 * 0.032 * cos 0)/( 710*9.8*0.0001)$

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3 years ago

How do I create an atom with a mass of 3 and a neutral charge?

kupik [55]

Answer:

a lithium atom (Z=3, A=7 AMU) contains three protons (found from Z), three electrons (as the number of protons is equal to the number of electrons in an atom), and four neutrons (7 – 3 = 4).

Explanation:

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2 years ago